Thanks @David_Brooks - 4) I'd attempted - mostly. 3) did not seem applicable since I constantly have basemaps not matching the coordinate system of features on the map. 2) and 5) were not applicable. So I tried 1) and my feature class was missing from the catalog somehow!
Turns out I messed up when creating the layer. Not 100% sure what I did, but when I opened a new project to troubleshoot per your recommendation, the feature class was not in the .gdb anymore. BUT there was a standalone table (excel or csv deal NOT an FC) of the same name. I think my previous zoom in zoom out debacle was using either the deleted FC from memory or the mystery table. I THINK the mystery table was the result of some geoprocessing I had done to create the culprit FC initially. The FC was a partial product of this:
with arcpy.da.SearchCursor(table_in, ['att1', 'SHAPE@XY'] as cursor:
for rw in cursor:
# extract centroid coords and proceed
#create new geometry called points and create new fc
#arcpy.CopyFeatures_management(points, fp_out
It may have been from not:
del cursor
del rw
After "arcpy.da.SearchCursor..." Despite the "With arcpy.da..." this post suggests (based off of ESRI docs) that we should STILL "del cursor/row" (https://gis.stackexchange.com/questions/254013/why-del-cursor-row-objects-of-arcpy).
So I added, reran and output a new culprit feature class which original produced the problem. Now it's working.
The recurrent problem of features disappearing is probably a separate issue of mine related to not closing an editing session properly. This situation was related to probably running flawed code multiple times and the Table of Contents referencing a Table that wasn't a Feature Class. Either due to not deleting cursors/rows or possibly just erroring out a couple times after the table was created incorrectly and not realizing it. Phhhheeewww- long winded. Thanks Brooks!